Drivers of the recent tropical expansion in the southern hemisphere: Changing SSTs or ozone depletion?

Darryn W. Waugh*, Chaim I. Garfinkel, Lorenzo M. Polvani

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

79 Scopus citations


Observational evidence indicates that the southern edge of the Hadley cell (HC) has shifted southward during austral summer in recent decades. However, there is no consensus on the cause of this shift, with several studies reaching opposite conclusions as to the relative role of changes in sea surface temperatures (SSTs) and stratospheric ozone depletion in causing this shift. Here, the authors perform a meta-analysis of the extant literature on this subject and quantitatively compare the results of all published studies that have used singleforcing model integrations to isolate the role of different factors on the HC expansion during austral summer. It is shown that the weight of the evidence clearly points to stratospheric ozone depletion as the dominant driver of the tropical summertime expansion over the period in which an ozone hole was formed (1979 to late 1990s), although SST trends have contributed to trends since then. Studies that have claimed SSTs as the major driver of tropical expansion since 1979 have used prescribed ozone fields that underrepresent the observed Antarctic ozone depletion.

Original languageAmerican English
Pages (from-to)6581-6586
Number of pages6
JournalJournal of Climate
Issue number16
StatePublished - 2015

Bibliographical note

Publisher Copyright:
© 2015 American Meteorological Society.


  • Hadley circulation
  • Ozone
  • Subsidence
  • Trends


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